The present invention relates to new and improved equipment for continuously measuring the length of endless material which is being wound upon a rotating core into a circular package, the machine comprising a movable member whose position depends upon the diameter of the circular package.
Measuring equipment of this type is disclosed in U.S. Pat. No. 4,024,645. There, the angular position of a swivel arm which bears upon a cylindrical yarn package formed on a yarn winding machine is mechanically transferred to the tap of a potentiometer whose setting controls the frequency of an oscillator. This frequency is transmitted, through a gate which is opened twice during respective 1.2 milliseconds intervals during each revolution of the winding coil, to a counter indicating the length of the wound-up yarn. The counter is reset by an adjustable device when a predetermined count is achieved, and the winding device is simultaneously stopped.
The potentiometer of this known measuring device, constituting part of a mechanoelectrical position sensor, is deficient insofar as the resistance member of the potentiometer is soon worn out by the thereon sliding contact member, which impedes any further exact measurement. This drawback is additionally intensified by the vibrations of the swivel arm occurring during the operation of the winding machine which are transmitted to the sliding contact member and soon cause the potentiometer to deteriorate or become useless.